Liebert Hisp - Cooling and Heating Unit; Unit with Freecooling

English
5
5.1.4 -- Optional ala rm card
Besides the components described for the standard configura-
tion, on the alarm card --- which can be supplied as optional ---
there are relay contacts to have the following alarms sepa-
rated:
1) Compressor high and low pressure
2) High temperature
3) Low temperature
4) Dirty filter alarm (if installed)
5) Fan fault
These alarms cause the unit to stop in the same ways as de-
scribed in the previous paragraph.
For a complete description of the alarms see the encl. Micro-
face manual.
5.1.5 -- Unit in stand--by
The control of the unit in stand---by is completely automatic
thanks to the possibility of connecting the Microface control. A
unit in stand---by starts in the event of an alarm st opping the
main unit; this occurs even if the main unit is switched off or dis-
appears from the system, due to a fault on the cont rol connect-
ing bus. The rotation of the units in stand ---by occurs automati-
cally every 24 hours, so as to allow a homogeneous wear of the
system components.
If the system is connected to the Hiromatic interface, it is pos-
sible to set a different rotation control.
If several units are simultaneously working with the same set
point, the temperature used for the control is the average of the
detected ones; further, in the operation with compressor, the
proportionalband is divided in as many parts as twicethe num-
ber of units belonging to the system,so as to shutthe totalavail-
able refrigerating capacity.
5.2 --- Coolin g and heatin g unit
5.2.1 -- Control logic
The control algorithm is based on a one---step adjustment for
the compressor---aided heating and cooling.
The control manages all its lags in the activation of the com-
pressor, as previously described, so as to guarantee its correct
operation and to make it function as long as possi ble.
Set Cooling °C
Cooling and
heating unit
Dead band!P@ Pband !P@ Pband
Heating
Fig. J --- Operation of the cooling + heating unit
5.2.2 -- Start--Stop
See Par. 5.1.2.
5.2.3 -- Alarm control
See Par. 5.1.3.
A further general warning is available signalling the following
abnormal condition:
S heater thermostat (reset on the thermostat).
Notes:
S the warning doesn’t cause the unit to stop.
S In case the safety heater thermostat intervenes, the reset
must be carried out on the thermostat, following the same
instructions as before.
5.2.4 -- Optional ala rm card
See Par. 5.1.4.
5.2.5 -- Unit in stand--by
See Par. 5.1.5.
5.3 --- Unit with Freecooling
5.3.1 -- Control logic
This option is also managed by the Microface microprocessor
control, which can be combined with the Hiromatic control to
monitor all the operation parameters of the unit (see the en-
closed manual). The control algorithm is based on a one---step
adjustment for the compressor---aided heating and cooling
and on an adjustment of a Proportional --- Integrative type for
cooling in the Freecooling mode with setting of the set point
and proportional band (P) (Fig. K).
The control manages all its lags in the activation of the com-
pressor, as seen in the two preceding cases, so as to guarantee
its correctoperationand tomake it function as long aspossible.
The Freec ooling mode is activated depending on the differ-
ence (which can be set) between the internal and the external
temperatures. This means that if the difference between the 2
temperatures increases beyond a certain value, the unit auto-
matically passes to the Freecooling function:the compressoris
de---activated and the analog output controls the 3---point ser-
vomotor of the damper. The damper opening is determined as
a function of the difference between the outside and inside
temperatures and as a function of the intake air temperature,
which cannot be lower than a preset safety value.
If the inside temperature exceeds the proportional band by
more than 20% for over 10 minutes, the unit shifts to the com-
pressor---aided cooling and the Freecooling mode remains
de---activated for ½ hour. If the inside temperature exceeds the
proportional band by more than 50% for over 2 minutes, the
Freecooling mode is de---activated for ½ hour, and the unit
shifts to cooling by means of the refrigerating compressor.
Set
CoolingHeating °C
Freecooling
mode
Compres-
sor
cooling mode
Dead band!P@ Pband !P@ Pband
Set
CoolingHeating °C
Dead band!P@ Pband !P@ Pband
Fig. K --- Operation of compressor, electric heaters and opening of
the Freecooling damper
5.3.2 -- Start--Stop
There are 2 ways for starting or stopping the unit:
a) the digital input of the Microface card;
b) the ON---OFF push button on the Hiromatic interface (op-
tional).
Priority with Hiromatic: a) and b) must be regarded as 2 series
cont acts; the unit can operate only if all contac ts are on.
5.3.3 -- Alarm control
The 2 alarm contacts available on theterminal board of the con-
trol panel can be used in this way:
1) General alarm:
S compressor low pressure
S compressor high pressure (reset on the pressure switch)
S senso r fault
S memory fault
S fan fault
2) General warning --- signalling of various abnormal condi-
tions, among which:
S high temperature
S low temperature
S heater thermostat (reset on the thermostat).